1. Field of the Invention
The present invention relates to a process for producing trifluoromethylpyridines directly from .alpha.-picoline, .gamma.-picoline and lutidines. In particular, it relates to a process for producing .alpha. or .gamma.-trifluoromethylpyridine, bis(trifluoromethyl)pyridines or chlorides having 1 to 3 chlorine atoms in their pyridine nucleus (hereinafter referring to as trifluoromethylpyridines) which comprises reacting .alpha.-picoline, .gamma.-picoline or lutidines (hereinafter referring to as pyridines) with chlorine and anhydrous hydrogen fluoride in the presence of diluent and special catalyst.
2. Description of the Prior Arts
The trifluoromethylpyridines are compounds useful as raw material for herbicide, insecticide and so on.
As conventional processes for producing the trifluoromethylpyridines, they have been known by U.S. Pat. Nos. 2,516,402 and 3,787,420 and WO Publication No. 79/00094 etc., however these processes are only experimental small scale.
In said U.S. Patents, there has been disclosed a process for producing the trifluoromethylpyridines which comprises (1) reacting the pyridines with chloride gas in a liquid phase under light radiation, or reacting them with chlorine gas in a vapor phase in the presence of a diluent at an elevated temperature to produce the corresponding trichloromethylpyridines and (2) reacting these trichloromethylpyridines with hydrogen fluoride in an autoclave, or an antimony trifluoride in a liquid phase. However, this chlorination step requires a long time for the reaction or produces a large quantity of by-products to be difficult to separate the object intermediates. This fluorination step requires also a long time for the reaction and a use of an autoclave or expensive antimony trifluoride. Therefore, it is not satisfactory as an industrial process.
Also, in said WO Publication, there has been disclosed a process for producing a trifluoromethylpyridine which comprises reacting a picolinic acid with sulfur tetrafluoride in the presence of hydrogen fluoride in an autoclave. However, the picolinic acid as a raw material is expensive and the sulfur tetrafluoride which is toxic to men and beasts is used. It requires also a long time for the reaction and a use of an autoclave. Therefore, it has many industrial disadvantages.